Potentiometer device

ABSTRACT

A potentiometer device including a resistor path and a conductive film spaced therefrom. The film may be brought in contact with the resistor by exerting finger pressure. The tap voltage is stored in a memory and displayed by means of LEDs.

BACKGROUND OF THE INVENTION

The present invention relates to a potentiometer device. Electricalpotentiometers have been known for many decades. They comprise aresistor path made of wire or carbon in circular or elongated shape anda tape member or slider movable along the resistor path and makingcontact therewith. Usually, the tap is manually moved and its positionmay be recognized.

Manual adjustment of a potentiometer takes some time, in particular if apredetermined tap position is to be made. Sometimes this delay isembarrassing. For example, in electronic musical instruments, theso-called "registration" is selected by means of potentiometers and hasto be readjusted during play. The handling may be facilitated byreplacing the potentiometers by sets of switches, but these, of course,have only a limited number of settings.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide apotentiometer device which can be rapidly set to any of its potentialsettings.

It is a further object of the present invention to provide such apotentiometer device with means permitting display of the selectedsetting.

In accordance with the present invention, the potentiometer devicecomprises a resistor path which preferably is of the strip-shaped,elongated form. an electrically conductive film member is mounted spacedabove the resistor path and may be brought in contact therewith byfinger pressure, the conductive film member forming the tap terminal ofthe potentiometer. The tap voltage is thus supplied only during thecontact or finger pressure interval, and the setting so selected is tobe memorized. The most simple memory, for example, would be asample-and-hold circuit, but it is preferred to connect the film memberto the input of an analog-to-digital converter and to load the output ofthe latter into a RAM (random access memory) which then holds a digitalvalue representative of the tap voltage. The number of digits of suchvalue determines how fine the setting can be made. Light emitting diodesmay be used to display the respective setting. In order to avoidfloating of the A/D converter input upon release of the film member, itis preferred to have the film member connected, via a resistor, to areference potential and to check by means of a comparator whether theactual voltage at the tap differs from said reference potential, and tostart a conversion cycle upon only a predetermined difference.

The optical display is useful not only in conjunction with manualsetting. Many modern electronic organs permit memorizing a registrationonce elaborated and reading the memorized settings into the internalmemory of the organ; light emitting diode displays may be easilycontrolled by such externally produced signals so that the player hasfull control of all his registers.

Preferred embodiments of the invention are illustrated in the attacheddrawings and will be explained hereunder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematically and not to scale the input and displayportion of the potentiometer device in section.

FIG. 2 is a partial plan view of the device of FIG. 1.

FIG. 3 is a block circuit diagram of the potentiometer device accordingto the invention including a plurality of input and display portions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first of FIG. 1 and FIG. 2, a support or substrate 10 carriesan elongated resistor path 12 and, lateral with respect thereto, aseries of light emitting diodes LED 14. A spacer film 16 is aperturedfor the LED and for the resistor path and insures that a film member 18contacts resistor path 12 only upon pressure exertion upon film member18 by exertion of pressure on flexible cover 20. The latter has anelectrically conductive layer on its side facing the resistor path. Theterminals of the LEDs extend through support 10 to the rear sidethereof. The described layout may, of course, be modified; for example,the LEDs may be mounted centrally with respect to two parallel resistorstrips, etc.

Referring now to FIG. 3, the device comprises sixteen registerpotentiometers of an electronic organ and allocated processingcircuitry. Of the sixteen resistor/film/LED units, only two, however,are depicted in FIG. 3. The taps are scanned in time multiplex. For thispurpose, the sixteen taps are connected to the analog inputs of analogmultiplexer 30 while the terminals of the sixteen resistors arerespectively connected to ground potential and to a supply voltage of,say, 5 volts. Upon finger pressure on the film member, accordingly, avoltage between 0 and 5 volts is fed to the respective multiplexerinput. The scanning is effected by means of clock generator 32 followedby a 4-bit counter 34.

The output of multiplexer 30 is applied to a load resistor of, say, 50ohms and to the input of a comparator 36 whose other input is connectedto ground. As long as a film member does not make contact with itsresistor path, both the comparator inputs are at ground potential sothat the comparator output does not produce a control signal.

Upon recognition of a potential difference at its inputs, comparator 36produces a START signal for analog-to-digital converter 38 whichconverts the analog output signal of multiplexer 30 into an 8-bitdigital signal. The respective address is given by counter 34, and undercontrol of a load command on line 40, output data of the converter arewritten into random access memory 42. The address given by counter 34 aswell as data read from memory 42 are used for the internal control ofthe musical instrument. Further, they are used for display control.

A decoder 44 fed with addresses from counter 34 provides a 4-into-16conversion and supplies a column driver circuit 46 while data from RAM42 supply a line driver circuit 48. The outputs of driver circuits 46,48 form a matrix in the intersections of which the LEDs are connected.In result, the LED series of each resistor/display unit indicates thepoint next to the site where the player touched in the film member.

It will be understood that the units disposed side by side may all sharea common substrate, a common spacer film, and a common transparent coverfilm because such a design reduces production costs. Also, the playermay set all units by one single finger stroke across all sixteen units.

It will be further understood that the display may be set also if thedata are not read from RAM 42 but are supplied by an exterior source.

We claim:
 1. A potentiometer device comprising:a support; a resistorpath disposed on a surface of said support and having first and secondend terminals for connection, respectively, to a reference voltage and asupply voltage of a voltage source; a plurality of lights mounted onsaid support adjacent to said resistor path so as to be visible; aspacer mounted on said support adjacent to said resistor path and saidplurality of lights; an electrically conductive film means coupled tosaid spacer and overlying said resistor path and mounted on said supportin alignment therewith but spaced therefrom, said film means for actingas a center tap terminal of said potentiometer device, said film meansfor elastically deforming in response to pressure so as to makeelectrical contact with said resistor path to form a voltage dividerwith the tap voltage of said electrically conductive film means relativeto said reference voltage being a function of the position along saidresistor path where said film means contacts said resistor path;processing means connected to said film means and to said plurality oflights for storing said tap voltage and for lighting an appropriategroup of one or more of said lights to visually indicate the relativemagnitude of said tap voltage generated on said film means when saidfilm means last touched said resistor path with said reference voltageand said supply voltage coupled to opposite ends of said resistor path;comparator means in said processing means, said comparator means havingone input coupled to said film means and coupled to a referencepotential through a load resistor and having one input coupled to apredetermined reference potential from a source other than saidpotentiometer device, said comparator means for generating a startsignal when the voltage on said film means differs from said referencepotential; and wherein each said light has two terminals which must becoupled to two signals at different voltages in order to light saidlight and wherein said processing means comprises a random access memoryand an analog-to-digital converter, said analog-to-digital converterhaving an analog voltage input and having a digital data output andhaving a control input coupled to said start signal such that conversionby said analog-to-digital converter starts when said start signal isactivated, the analog voltage input of said analog-to-digital converterbeing coupled to said conductive film means, and said digital dataoutput thereof being coupled to said random access memory so as to storea digital value representing said center tap voltage in said randomaccess memory and said processing means further comprising acounter/clock means coupled to generate address signals for controllingstorage of digital data from said analog to digital converter in saidrandom access memory, and further comprising a decoder/column drivermeans coupled to said lights and to said counter/clock means forgenerating one of said two signals needed to light the appropriatelight, and further comprising line driver means coupled to the output ofsaid random access memory means to supply the other of said two signalsneeded to light the appropriate light.
 2. A potentiometer devicecomprising:a support; a resistor path disposed on a surface of saidsupport and having first and second end terminals for connection,respectively, to a reference voltage and a supply voltage of a voltagesource; a plurality of lights mounted on said support adjacent to saidresistor path so as to be visible; a spacer mounted on said supportadjacent to said resistor path and said plurality of lights; anelectrically conductive film means coupled to said spacer and overlyingsaid resistor path and mounted on said support in alignment therewithbut spaced therefrom, said film means for acting as a center tapterminal of said potentiometer device, said film means for elasticallydeforming in response to pressure so as to make electrical contact withsaid resistor path to form a voltage divider with the tap voltage ofsaid electrically conductive film means relative to said referencevoltage being a function of the position along said resistor path wheresaid film means contacts said resistor path; processing means connectedto said film means and to said plurality of lights for storing said tapvoltage and for lighting an appropriate group of one or more of saidlights to visually indicate the relative magnitude of said tap voltagegenerated on said film means when said film means last touched saidresistor path with said reference voltage and said supply voltagecoupled to opposite ends of said resistor path; comparator means in saidprocessing means, said comparator means having one input coupled to saidfilm means and coupled to a reference potential through a load resistorand having one input coupled to a predetermined reference potential froma source other than said potentiometer device, said comparator means forgenerating a start signal when the voltage on said film means differsfrom said reference potential; and wherein each said light has twoterminals which must be coupled to two signals at different voltages inorder to light said light and wherein said processing means comprises arandom access memory and an analog-to-digital converter, saidanalog-to-digital converter having an analog voltage input and having adigital data output and having a control input coupled to said startsignal such that conversion by said analog-to-digital converter meansstarts when said start signal is activated, the analog voltage input ofsaid analog-to-digital converter being coupled to said conductive filmmeans, and said digital data output thereof being coupled to said randomaccess memory so as to store a digital value representing said centertap voltage in said random access memory, said processing means furthercomprising a counter/clock means coupled to generate address signals forcontrolling storage of digital data from said analog-to-digitalconverter in said random access memory, and further comprising adecoder/column driver means coupled to said lights and to saidcounter/clock means for generating one of said two signals needed tolight the appropriate light, and further comprising line driver meanscoupled to the output of said random access memory means to supply theother of said two signals needed to light the appropriate light; andfurther comprising a multiplexer means having a select control inputcoupled to said counter/clock means and having a plurality of signalchannel inputs for coupling to a plurality of film means of otherpotentiometer devices and having an output coupled to one input of saidcomparator, said multiplexer means for switching the signal channelinput selected by address signals from said counter/clock means to be inelectrical connection with said output.